Supporting multicast over a network domain

ABSTRACT

Various example embodiments relate generally to supporting Multiprotocol Label Switching (MPLS)-based multicast over a Bit Index Explicit Replication (BIER) domain. Various example embodiments for supporting MPLS-based multicast over a BIER domain may be configured to support MPLS point-to-multipoint (P2MP) label switched paths (LSPs) over a BIER domain. Various example embodiments for supporting MPLS-based multicast over a BIER domain may be configured to support establishment and transport of P2MP LSPs over a BIER domain (e.g., signaling MPLS via the BIER domain, stitching the MPLS datapath to the BIER domain based on identification of P2MP LSPs within the BIER domain, and so forth).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/024,084, filed on Jun. 29, 2018, entitled SUPPORTING MULTICAST OVER ANETWORK DOMAIN, which is hereby incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to communication networks and,more particularly but not exclusively, to supporting multicast incommunication networks.

BACKGROUND

Multicast is used in many types of communication networks to delivervarious types of information.

SUMMARY

Various example embodiments relate generally to supporting MultiprotocolLabel Switching (MPLS)-based multicast via a Bit Index ExplicitReplication (BIER) domain.

In at least some example embodiments, an apparatus is provided. In atleast some example embodiments, the apparatus includes at least oneprocessor and at least one memory including computer program code,wherein the at least one memory and the computer program code areconfigured to, with the at least one processor, cause the apparatus toat least receive, by a BIER border router (BBR) of a BIER domain from anMPLS domain, MPLS signaling information associated with apoint-to-multipoint (P2MP) label switched path (LSP) and send, by theBBR toward a device configured to assign a BIER tree label (BTL)identifying the P2MP LSP within the BIER domain, the MPLS signalinginformation associated with the P2MP LSP. In at least some exampleembodiments, the MPLS signaling information is received as MultiprotocolLabel Distribution Protocol (mLDP) signaling. In at least some exampleembodiments, the MPLS signaling information includes a forwardingequivalence class (FEC) and an action. In at least some exampleembodiments, the MPLS signaling information is sent in a BIER signalingpacket. In at least some example embodiments, the device configured toassign the BTL identifying the P2MP LSP within the BIER domain is acontroller of the BIER domain or an egress BBR (EBBR) of the BIERdomain. In at least some example embodiments, the at least one memoryand the computer program code are configured to, with the at least oneprocessor, cause the apparatus to at least determine, by the BBR,whether the root of the P2MP LSP is located across the BIER domain fromthe BBR. In at least some example embodiments, the at least one memoryand the computer program code are configured to, with the at least oneprocessor, cause the apparatus to at least receive, by the BBR from thedevice configured to assign the BTL identifying the P2MP LSP within theBIER domain, the BTL identifying the P2MP LSP within the BIER domain andconfigure, by the BBR based on the BTL identifying the P2MP LSP withinthe BIER domain, an entry indicative of handling of packets of the P2MPLSP within the MPLS domain. In at least some example embodiments, theentry indicative of handling of packets of the P2MP LSP within the MPLSdomain includes an indication of an MPLS label identifying the P2MP LSPwithin the MPLS domain. In at least some example embodiments, the atleast one memory and the computer program code are configured to, withthe at least one processor, cause the apparatus to at least receive, bythe BBR via the BIER domain, a packet of the P2MP LSP that includes theBTL identifying the P2MP LSP within the BIER domain, modify, by the BBR,the packet of the P2MP LSP to replace the BTL identifying the P2MP LSPwithin the BIER domain with an MPLS label identifying the P2MP LSPwithin the MPLS domain to provide a modified packet, and send, by theBBR via the MPLS domain, the modified packet. In at least some exampleembodiments, an apparatus includes at least one processor and at leastone memory including computer program code, wherein the at least onememory and the computer program code are configured to, with the atleast one processor, cause the apparatus to at least receive, by aborder router of a multicast explicit replication domain from amulticast label switching domain, multicast signaling informationassociated with a multicast label switched path and send, by the borderrouter toward a device configured to assign a tree label identifying themulticast label switched path within the multicast explicit replicationdomain, the multicast signaling information associated with themulticast label switched path.

In at least some example embodiments, a method is provided. In at leastsome example embodiments, the method includes receiving, by a BIERborder router (BBR) of a BIER domain from an MPLS domain, MPLS signalinginformation associated with a point-to-multipoint (P2MP) label switchedpath (LSP) and sending, by the BBR toward a device configured to assigna BIER tree label (BTL) identifying the P2MP LSP within the BIER domain,the MPLS signaling information associated with the P2MP LSP. In at leastsome example embodiments, the MPLS signaling information is received asMultiprotocol Label Distribution Protocol (mLDP) signaling. In at leastsome example embodiments, the MPLS signaling information includes aforwarding equivalence class (FEC) and an action. In at least someexample embodiments, the MPLS signaling information is sent in a BIERsignaling packet. In at least some example embodiments, the deviceconfigured to assign the BTL identifying the P2MP LSP within the BIERdomain is a controller of the BIER domain or an egress BBR (EBBR) of theBIER domain. In at least some example embodiments, the method includesdetermining, by the BBR, whether the root of the P2MP LSP is locatedacross the BIER domain from the BBR. In at least some exampleembodiments, the method includes receiving, by the BBR from the deviceconfigured to assign the BTL identifying the P2MP LSP within the BIERdomain, the BTL identifying the P2MP LSP within the BIER domain andconfiguring, by the BBR based on the BTL identifying the P2MP LSP withinthe BIER domain, an entry indicative of handling of packets of the P2MPLSP within the MPLS domain. In at least some example embodiments, theentry indicative of handling of packets of the P2MP LSP within the MPLSdomain includes an indication of an MPLS label identifying the P2MP LSPwithin the MPLS domain. In at least some example embodiments, the methodincludes receiving, by the BBR via the BIER domain, a packet of the P2MPLSP that includes the BTL identifying the P2MP LSP within the BIERdomain, modifying, by the BBR, the packet of the P2MP LSP to replace theBTL identifying the P2MP LSP within the BIER domain with an MPLS labelidentifying the P2MP LSP within the MPLS domain to provide a modifiedpacket, and sending, by the BBR via the MPLS domain, the modifiedpacket. In at least some example embodiments, a method includesreceiving, by a border router of a multicast explicit replication domainfrom a multicast label switching domain, multicast signaling informationassociated with a multicast label switched path and sending, by theborder router toward a device configured to assign a tree labelidentifying the multicast label switched path within the multicastexplicit replication domain, the multicast signaling informationassociated with the multicast label switched path.

In at least some example embodiments, a non-transitory computer readablemedium is provided. In at least some example embodiments, thenon-transitory computer-readable medium includes program instructionsfor causing an apparatus to at least receive, by a BIER border router(BBR) of a BIER domain from an MPLS domain, MPLS signaling informationassociated with a point-to-multipoint (P2MP) label switched path (LSP)and send, by the BBR toward a device configured to assign a BIER treelabel (BTL) identifying the P2MP LSP within the BIER domain, the MPLSsignaling information associated with the P2MP LSP. In at least someexample embodiments, the MPLS signaling information is received asMultiprotocol Label Distribution Protocol (mLDP) signaling. In at leastsome example embodiments, the MPLS signaling information includes aforwarding equivalence class (FEC) and an action. In at least someexample embodiments, the MPLS signaling information is sent in a BIERsignaling packet. In at least some example embodiments, the deviceconfigured to assign the BTL identifying the P2MP LSP within the BIERdomain is a controller of the BIER domain or an egress BBR (EBBR) of theBIER domain. In at least some example embodiments, the non-transitorycomputer-readable medium includes program instructions for causing theapparatus to at least determine, by the BBR, whether the root of theP2MP LSP is located across the BIER domain from the BBR. In at leastsome example embodiments, the non-transitory computer-readable mediumincludes program instructions for causing the apparatus to at leastreceive, by the BBR from the device configured to assign the BTLidentifying the P2MP LSP within the BIER domain, the BTL identifying theP2MP LSP within the BIER domain and configure, by the BBR based on theBTL identifying the P2MP LSP within the BIER domain, an entry indicativeof handling of packets of the P2MP LSP within the MPLS domain. In atleast some example embodiments, the entry indicative of handling ofpackets of the P2MP LSP within the MPLS domain includes an indication ofan MPLS label identifying the P2MP LSP within the MPLS domain. In atleast some example embodiments, the non-transitory computer-readablemedium includes program instructions for causing the apparatus to atleast receive, by the BBR via the BIER domain, a packet of the P2MP LSPthat includes the BTL identifying the P2MP LSP within the BIER domain,modify, by the BBR, the packet of the P2MP LSP to replace the BTLidentifying the P2MP LSP within the BIER domain with an MPLS labelidentifying the P2MP LSP within the MPLS domain to provide a modifiedpacket, and send, by the BBR via the MPLS domain, the modified packet.In a non-transitory computer-readable medium includes programinstructions for causing an apparatus to at least receive, by a borderrouter of a multicast explicit replication domain from a multicast labelswitching domain, multicast signaling information associated with amulticast label switched path and send, by the border router toward adevice configured to assign a tree label identifying the multicast labelswitched path within the multicast explicit replication domain, themulticast signaling information associated with the multicast labelswitched path.

In at least some example embodiments, an apparatus is provided. In atleast some example embodiments, the apparatus includes means forreceiving, by a BIER border router (BBR) of a BIER domain from an MPLSdomain, MPLS signaling information associated with a point-to-multipoint(P2MP) label switched path (LSP) and means for sending, by the BBRtoward a device configured to assign a BIER tree label (BTL) identifyingthe P2MP LSP within the BIER domain, the MPLS signaling informationassociated with the P2MP LSP. In at least some example embodiments, theMPLS signaling information is received as Multiprotocol LabelDistribution Protocol (mLDP) signaling. In at least some exampleembodiments, the MPLS signaling information includes a forwardingequivalence class (FEC) and an action. In at least some exampleembodiments, the MPLS signaling information is sent in a BIER signalingpacket. In at least some example embodiments, the device configured toassign the BTL identifying the P2MP LSP within the BIER domain is acontroller of the BIER domain or an egress BBR (EBBR) of the BIERdomain. In at least some example embodiments, the apparatus includesmeans for determining, by the BBR, whether the root of the P2MP LSP islocated across the BIER domain from the BBR. In at least some exampleembodiments, the apparatus includes means for receiving, by the BBR fromthe device configured to assign the BTL identifying the P2MP LSP withinthe BIER domain, the BTL identifying the P2MP LSP within the BIER domainand means for configuring, by the BBR based on the BTL identifying theP2MP LSP within the BIER domain, an entry indicative of handling ofpackets of the P2MP LSP within the MPLS domain. In at least some exampleembodiments, the entry indicative of handling of packets of the P2MP LSPwithin the MPLS domain includes an indication of an MPLS labelidentifying the P2MP LSP within the MPLS domain. In at least someexample embodiments, the apparatus includes means for receiving, by theBBR via the BIER domain, a packet of the P2MP LSP that includes the BTLidentifying the P2MP LSP within the BIER domain, means for modifying, bythe BBR, the packet of the P2MP LSP to replace the BTL identifying theP2MP LSP within the BIER domain with an MPLS label identifying the P2MPLSP within the MPLS domain to provide a modified packet, and means forsending, by the BBR via the MPLS domain, the modified packet. In atleast some example embodiments, an apparatus includes means forreceiving, by a border router of a multicast explicit replication domainfrom a multicast label switching domain, multicast signaling informationassociated with a multicast label switched path and means for sending,by the border router toward a device configured to assign a tree labelidentifying the multicast label switched path within the multicastexplicit replication domain, the multicast signaling informationassociated with the multicast label switched path.

In at least some example embodiments, an apparatus is provided. In atleast some example embodiments, the apparatus includes at least oneprocessor and at least one memory including computer program code,wherein the at least one memory and the computer program code areconfigured to, with the at least one processor, cause the apparatus toat least receive, by a device associated with a BIER domain, MPLSsignaling information associated with a point-to-multipoint (P2MP) labelswitched path (LSP) and assign, by the device based on the MPLSsignaling information associated with the P2MP LSP, a BIER tree label(BTL) identifying the P2MP LSP within the BIER domain. In at least someexample embodiments, the MPLS signaling information is received from aningress BIER border router (IBBR) of the BIER domain. In at least someexample embodiments, the MPLS signaling information is received in aBIER signaling packet. In at least some example embodiments, the MPLSsignaling information includes a forwarding equivalence class (FEC) andan action. In at least some example embodiments, the device associatedwith the BIER domain is a controller of the BIER domain or an egressBIER border router (EBBR) of the BIER domain for the P2MP LSP. In atleast some example embodiments, the device associated with the BIERdomain is a controller of the BIER domain. In at least some exampleembodiments, the at least one memory and the computer program code areconfigured to, with the at least one processor, cause the apparatus toat least send, from the device toward one or more BIER border routers(BBRs) interested in the P2MP LSP, the BTL identifying the P2MP LSPwithin the BIER domain. In at least some example embodiments, the one ormore BBRs interested in the P2MP LSP include an ingress BBR (IBBR) fromwhich the MPLS signaling information is received and an egress BBR(EBBR) of the BIER domain for the P2MP LSP. In at least some exampleembodiments, the device associated with the BIER domain is an egressBIER border router (EBBR) of the BIER domain for the P2MP LSP. In atleast some example embodiments, the at least one memory and the computerprogram code are configured to, with the at least one processor, causethe apparatus to at least send, from the device toward a controller ofthe BIER domain, the BTL identifying the P2MP LSP within the BIERdomain. In at least some example embodiments, the at least one memoryand the computer program code are configured to, with the at least oneprocessor, cause the apparatus to at least assign, by the device, anMPLS label identifying the P2MP LSP within an MPLS domain and send, bythe device toward a root of the P2MP LSP via the MPLS domain, the MPLSlabel identifying the P2MP LSP within the MPLS domain. In at least someexample embodiments, an apparatus includes at least one processor and atleast one memory including computer program code, wherein the at leastone memory and the computer program code are configured to, with the atleast one processor, cause the apparatus to at least receive, by adevice associated with a multicast explicit replication domain,multicast signaling information associated with a multicast labelswitched path and assign, by the device based on the multicast signalinginformation associated with the multicast label switched path, a treelabel identifying the multicast label switched path within the multicastexplicit replication domain.

In at least some example embodiments, a method is provided. In at leastsome example embodiments, the method includes receiving, by a deviceassociated with a BIER domain, MPLS signaling information associatedwith a point-to-multipoint (P2MP) label switched path (LSP) andassigning, by the device based on the MPLS signaling informationassociated with the P2MP LSP, a BIER tree label (BTL) identifying theP2MP LSP within the BIER domain. In at least some example embodiments,the MPLS signaling information is received from an ingress BIER borderrouter (IBBR) of the BIER domain. In at least some example embodiments,the MPLS signaling information is received in a BIER signaling packet.In at least some example embodiments, the MPLS signaling informationincludes a forwarding equivalence class (FEC) and an action. In at leastsome example embodiments, the device associated with the BIER domain isa controller of the BIER domain or an egress BIER border router (EBBR)of the BIER domain for the P2MP LSP. In at least some exampleembodiments, the device associated with the BIER domain is a controllerof the BIER domain. In at least some example embodiments, the methodincludes sending, from the device toward one or more BIER border routers(BBRs) interested in the P2MP LSP, the BTL identifying the P2MP LSPwithin the BIER domain. In at least some example embodiments, the one ormore BBRs interested in the P2MP LSP include an ingress BBR (IBBR) fromwhich the MPLS signaling information is received and an egress BBR(EBBR) of the BIER domain for the P2MP LSP. In at least some exampleembodiments, the device associated with the BIER domain is an egressBIER border router (EBBR) of the BIER domain for the P2MP LSP. In atleast some example embodiments, the method includes sending, from thedevice toward a controller of the BIER domain, the BTL identifying theP2MP LSP within the BIER domain. In at least some example embodiments,the method includes assigning, by the device, an MPLS label identifyingthe P2MP LSP within an MPLS domain and sending, by the device toward aroot of the P2MP LSP via the MPLS domain, the MPLS label identifying theP2MP LSP within the MPLS domain. In at least some example embodiments, amethod includes receiving, by a device associated with a multicastexplicit replication domain, multicast signaling information associatedwith a multicast label switched path and assigning, by the device basedon the multicast signaling information associated with the multicastlabel switched path, a tree label identifying the multicast labelswitched path within the multicast explicit replication domain.

In at least some example embodiments, a non-transitory computer readablemedium is provided. In at least some example embodiments, thenon-transitory computer-readable medium includes program instructionsfor causing an apparatus to at least receive, by a device associatedwith a BIER domain, MPLS signaling information associated with apoint-to-multipoint (P2MP) label switched path (LSP) and assign, by thedevice based on the MPLS signaling information associated with the P2MPLSP, a BIER tree label (BTL) identifying the P2MP LSP within the BIERdomain. In at least some example embodiments, the MPLS signalinginformation is received from an ingress BIER border router (IBBR) of theBIER domain. In at least some example embodiments, the MPLS signalinginformation is received in a BIER signaling packet. In at least someexample embodiments, the MPLS signaling information includes aforwarding equivalence class (FEC) and an action. In at least someexample embodiments, the device associated with the BIER domain is acontroller of the BIER domain or an egress BIER border router (EBBR) ofthe BIER domain for the P2MP LSP. In at least some example embodiments,the device associated with the BIER domain is a controller of the BIERdomain. In at least some example embodiments, the non-transitorycomputer-readable medium includes program instructions for causing theapparatus to at least send, from the device toward one or more BIERborder routers (BBRs) interested in the P2MP LSP, the BTL identifyingthe P2MP LSP within the BIER domain. In at least some exampleembodiments, the one or more BBRs interested in the P2MP LSP include aningress BBR (IBBR) from which the MPLS signaling information is receivedand an egress BBR (EBBR) of the BIER domain for the P2MP LSP. In atleast some example embodiments, the device associated with the BIERdomain is an egress BIER border router (EBBR) of the BIER domain for theP2MP LSP. In at least some example embodiments, the non-transitorycomputer-readable medium includes program instructions for causing theapparatus to at least send, from the device toward a controller of theBIER domain, the BTL identifying the P2MP LSP within the BIER domain. Inat least some example embodiments, the non-transitory computer-readablemedium includes program instructions for causing the apparatus to atleast assign, by the device, an MPLS label identifying the P2MP LSPwithin an MPLS domain and send, by the device toward a root of the P2MPLSP via the MPLS domain, the MPLS label identifying the P2MP LSP withinthe MPLS domain. In at least some example embodiments, a non-transitorycomputer-readable medium includes program instructions for causing anapparatus to at least receive, by a device associated with a multicastexplicit replication domain, multicast signaling information associatedwith a multicast label switched path and assign, by the device based onthe multicast signaling information associated with the multicast labelswitched path, a tree label identifying the multicast label switchedpath within the multicast explicit replication domain.

In at least some example embodiments, an apparatus is provided. In atleast some example embodiments, the apparatus includes means forreceiving, by a device associated with a BIER domain, MPLS signalinginformation associated with a point-to-multipoint (P2MP) label switchedpath (LSP) and means for assigning, by the device based on the MPLSsignaling information associated with the P2MP LSP, a BIER tree label(BTL) identifying the P2MP LSP within the BIER domain. In at least someexample embodiments, the MPLS signaling information is received from aningress BIER border router (IBBR) of the BIER domain. In at least someexample embodiments, the MPLS signaling information is received in aBIER signaling packet. In at least some example embodiments, the MPLSsignaling information includes a forwarding equivalence class (FEC) andan action. In at least some example embodiments, the device associatedwith the BIER domain is a controller of the BIER domain or an egressBIER border router (EBBR) of the BIER domain for the P2MP LSP. In atleast some example embodiments, the device associated with the BIERdomain is a controller of the BIER domain. In at least some exampleembodiments, the apparatus includes means for sending, from the devicetoward one or more BIER border routers (BBRs) interested in the P2MPLSP, the BTL identifying the P2MP LSP within the BIER domain. In atleast some example embodiments, the one or more BBRs interested in theP2MP LSP include an ingress BBR (IBBR) from which the MPLS signalinginformation is received and an egress BBR (EBBR) of the BIER domain forthe P2MP LSP. In at least some example embodiments, the deviceassociated with the BIER domain is an egress BIER border router (EBBR)of the BIER domain for the P2MP LSP. In at least some exampleembodiments, the apparatus includes means for sending, from the devicetoward a controller of the BIER domain, the BTL identifying the P2MP LSPwithin the BIER domain. In at least some example embodiments, theapparatus includes means for assigning, by the device, an MPLS labelidentifying the P2MP LSP within an MPLS domain and means for sending, bythe device toward a root of the P2MP LSP via the MPLS domain, the MPLSlabel identifying the P2MP LSP within the MPLS domain. In at least someexample embodiments, an apparatus includes means for receiving, by adevice associated with a multicast explicit replication domain,multicast signaling information associated with a multicast labelswitched path and means for assigning, by the device based on themulticast signaling information associated with the multicast labelswitched path, a tree label identifying the multicast label switchedpath within the multicast explicit replication domain.

In at least some example embodiments, an apparatus is provided. In atleast some example embodiments, the apparatus includes at least oneprocessor and at least one memory including computer program code,wherein the at least one memory and the computer program code areconfigured to, with the at least one processor, cause the apparatus toat least obtain, by a BIER border router (BBR) of a BIER domain, a BIERtree label (BTL) identifying a point-to-multipoint (P2MP) label switchedpath (LSP) within the BIER domain. In at least some example embodiments,to obtain BTL identifying the P2MP LSP within the BIER domain, the atleast one memory and the computer program code are configured to, withthe at least one processor, cause the apparatus to at least receive, bythe device from a controller of the BIER domain, the BTL identifying theP2MP LSP within the BIER domain. In at least some example embodiments,to obtain the BTL identifying the P2MP LSP within the BIER domain, theat least one memory and the computer program code are configured to,with the at least one processor, cause the apparatus to at leastreceive, by the device from an ingress BBR of the BIER domain, MPLSsignaling information including a forwarding equivalence class (FEC)associated with the P2MP LSP and assign, by the device based on the FECassociated with the P2MP LSP, the BTL identifying the P2MP LSP withinthe BIER domain. In at least some example embodiments, the FECassociated with the P2MP LSP is received in a BIER signaling packet. Inat least some example embodiments, the at least one memory and thecomputer program code are configured to, with the at least oneprocessor, cause the apparatus to at least send, by the device toward acontroller of the BIER domain, the BTL identifying the P2MP LSP withinthe BIER domain. In at least some example embodiments, the at least onememory and the computer program code are configured to, with the atleast one processor, cause the apparatus to at least send, by the devicetoward the IBBR of the BIER domain, the BTL identifying the P2MP LSPwithin the BIER domain. In at least some example embodiments, the BTLidentifying the P2MP LSP within the BIER domain is sent based on atleast one of a Multiprotocol-Border Gateway Protocol (MP-BGP) adjacency,a BGP Multicast Virtual Private Network (MVPN), or SegmentRouting-Traffic Engineering (SR-TE). In at least some exampleembodiments, an apparatus includes at least one processor and at leastone memory including computer program code, wherein the at least onememory and the computer program code are configured to, with the atleast one processor, cause the apparatus to at least obtain, by a borderrouter of a multicast explicit replication domain, a tree labelidentifying a multicast label switched path within the multicastexplicit replication domain.

In at least some example embodiments, a method is provided. In at leastsome example embodiments, the method includes obtaining, by a BIERborder router (BBR) of a BIER domain, a BIER tree label (BTL)identifying a point-to-multipoint (P2MP) label switched path (LSP)within the BIER domain. In at least some example embodiments, obtainingthe BTL identifying the P2MP LSP within the BIER domain includesreceiving, by the device from a controller of the BIER domain, the BTLidentifying the P2MP LSP within the BIER domain. In at least someexample embodiments, obtaining the BTL identifying the P2MP LSP withinthe BIER domain includes receiving, by the device from an ingress BBR ofthe BIER domain, MPLS signaling information including a forwardingequivalence class (FEC) associated with the P2MP LSP and assigning, bythe device based on the FEC associated with the P2MP LSP, the BTLidentifying the P2MP LSP within the BIER domain. In at least someexample embodiments, the FEC associated with the P2MP LSP is received ina BIER signaling packet. In at least some example embodiments, themethod includes sending, by the device toward a controller of the BIERdomain, the BTL identifying the P2MP LSP within the BIER domain. In atleast some example embodiments, the method includes sending, by thedevice toward the IBBR of the BIER domain, the BTL identifying the P2MPLSP within the BIER domain. In at least some example embodiments, theBTL identifying the P2MP LSP within the BIER domain is sent based on atleast one of a Multiprotocol-Border Gateway Protocol (MP-BGP) adjacency,a BGP Multicast Virtual Private Network (MVPN), or SegmentRouting-Traffic Engineering (SR-TE). In at least some exampleembodiments, a method includes obtaining, by a border router of amulticast explicit replication domain, a tree label identifying amulticast label switched path within the multicast explicit replicationdomain.

In at least some example embodiments, a non-transitory computer readablemedium is provided. In at least some example embodiments, thenon-transitory computer-readable medium includes program instructionsfor causing an apparatus to at least obtain, by a BIER border router(BBR) of a BIER domain, a BIER tree label (BTL) identifying apoint-to-multipoint (P2MP) label switched path (LSP) within the BIERdomain. In at least some example embodiments, to obtain BTL identifyingthe P2MP LSP within the BIER domain, the non-transitorycomputer-readable medium includes program instructions for causing theapparatus to at least receive, by the device from a controller of theBIER domain, the BTL identifying the P2MP LSP within the BIER domain. Inat least some example embodiments, to obtain the BTL identifying theP2MP LSP within the BIER domain, the non-transitory computer-readablemedium includes program instructions for causing the apparatus to atleast receive, by the device from an ingress BBR of the BIER domain,MPLS signaling information including a forwarding equivalence class(FEC) associated with the P2MP LSP and assign, by the device based onthe FEC associated with the P2MP LSP, the BTL identifying the P2MP LSPwithin the BIER domain. In at least some example embodiments, the FECassociated with the P2MP LSP is received in a BIER signaling packet. Inat least some example embodiments, the non-transitory computer-readablemedium includes program instructions for causing the apparatus to atleast send, by the device toward a controller of the BIER domain, theBTL identifying the P2MP LSP within the BIER domain. In at least someexample embodiments, the non-transitory computer-readable mediumincludes program instructions for causing the apparatus to at leastsend, by the device toward the IBBR of the BIER domain, the BTLidentifying the P2MP LSP within the BIER domain. In at least someexample embodiments, the BTL identifying the P2MP LSP within the BIERdomain is sent based on at least one of a Multiprotocol-Border GatewayProtocol (MP-BGP) adjacency, a BGP Multicast Virtual Private Network(MVPN), or Segment Routing-Traffic Engineering (SR-TE). In at least someexample embodiments, a non-transitory computer-readable medium includesprogram instructions for causing an apparatus to at least obtain, by aborder router of a multicast explicit replication domain, a tree labelidentifying a multicast label switched path within the multicastexplicit replication domain.

In at least some example embodiments, an apparatus is provided. In atleast some example embodiments, the apparatus includes means forobtaining, by a BIER border router (BBR) of a BIER domain, a BIER treelabel (BTL) identifying a point-to-multipoint (P2MP) label switched path(LSP) within the BIER domain. In at least some example embodiments, themeans for obtaining the BTL identifying the P2MP LSP within the BIERdomain includes means for receiving, by the device from a controller ofthe BIER domain, the BTL identifying the P2MP LSP within the BIERdomain. In at least some example embodiments, the means for obtainingthe BTL identifying the P2MP LSP within the BIER domain includes meansfor receiving, by the device from an ingress BBR of the BIER domain,MPLS signaling information including a forwarding equivalence class(FEC) associated with the P2MP LSP and means for assigning, by thedevice based on the FEC associated with the P2MP LSP, the BTLidentifying the P2MP LSP within the BIER domain. In at least someexample embodiments, the FEC associated with the P2MP LSP is received ina BIER signaling packet. In at least some example embodiments, theapparatus includes means for sending, by the device toward a controllerof the BIER domain, the BTL identifying the P2MP LSP within the BIERdomain. In at least some example embodiments, the apparatus includesmeans for sending, by the device toward the IBBR of the BIER domain, theBTL identifying the P2MP LSP within the BIER domain. In at least someexample embodiments, the BTL identifying the P2MP LSP within the BIERdomain is sent based on at least one of a Multiprotocol-Border GatewayProtocol (MP-BGP) adjacency, a BGP Multicast Virtual Private Network(MVPN), or Segment Routing-Traffic Engineering (SR-TE). In at least someexample embodiments, an apparatus includes means for obtaining, by aborder router of a multicast explicit replication domain, a tree labelidentifying a multicast label switched path within the multicastexplicit replication domain.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings herein can be readily understood by considering thefollowing detailed description in conjunction with the accompanyingdrawings, in which:

FIG. 1 depicts a communication system configured to support a P2MP LSPvia a BIER domain based on assignment of a label in the BIER domain thatuniquely identifies P2MP LSP within the BIER domain;

FIG. 2 depicts a communication system for illustrating assignment of alabel to a P2MP LSP, for uniquely identifying the P2MP LSP within theBIER domain, by a controller of the BIER domain;

FIG. 3 depicts a communication system for illustrating assignment of alabel to a P2MP LSP, for uniquely identifying the P2MP LSP within theBIER domain, by a BIER border router (BBR) of the BIER domain;

FIG. 4 depicts a communication system for illustrating assignment of alabel to a P2MP LSP, for uniquely identifying the P2MP LSP within theBIER domain, by a BIER border router (BBR) of the BIER domain;

FIG. 5 depicts a communication system for illustrating transport of MPLSpackets of a P2MP LSP across a BIER domain based on assignment of alabel to the P2MP LSP for uniquely identifying the P2MP LSP within theBIER domain;

FIG. 6 depicts an example embodiment of a method for use by an IBBR forsupporting assignment of a label to a P2MP LSP within a BIER domain foruniquely identifying the P2MP LSP within the BIER domain;

FIG. 7 depicts an example embodiment of a method for use by a BTLassigning node for supporting assignment of a label to a P2MP LSP withina BIER domain for uniquely identifying the P2MP LSP within the BIERdomain;

FIG. 8 depicts an example embodiment of a method for use by an EBBR forsupporting assignment of a label to a P2MP LSP within a BIER domain foruniquely identifying the P2MP LSP within the BIER domain;

FIG. 9 depicts an example embodiment of a method for use by borderrouter of a multicast explicit replication domain for supportingassignment of a label to a multicast label switched path within themulticast explicit replication domain for uniquely identifying themulticast label switched path within the multicast explicit replicationdomain;

FIG. 10 depicts an example embodiment of a method for use by anassigning node of a multicast explicit replication domain for supportingassignment of a label to a multicast label switched path within themulticast explicit replication domain for uniquely identifying themulticast label switched path within the multicast explicit replicationdomain;

FIG. 11 depicts an example embodiment of a method for use by a borderrouter of a multicast explicit replication domain for supportingassignment of a label to a multicast label switched path within themulticast explicit replication domain for uniquely identifying themulticast label switched path within the multicast explicit replicationdomain; and

FIG. 12 depicts a high-level block diagram of a computer suitable foruse in performing various functions presented herein.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

Various example embodiments relate generally to supporting MultiprotocolLabel Switching (MPLS)-based multicast over a Bit Index ExplicitReplication (BIER) domain. Various example embodiments for supportingMPLS-based multicast over a BIER domain may be configured to supportMPLS point-to-multipoint (P2MP) label switched paths (LSPs) over a BIERdomain. Various example embodiments for supporting MPLS-based multicastover a BIER domain may be configured to support establishment andtransport of P2MP LSPs over a BIER domain (e.g., signaling MPLS via theBIER domain, stitching the MPLS datapath to the BIER domain based onidentification of P2MP LSPs within the BIER domain, and so forth).Various example embodiments for supporting MPLS-based multicast over aBIER domain may be configured to support signaling of MPLS via the BIERdomain based on termination of MPLS signaling at the edge of the BIERdomain and forwarding of MPLS signaling information from the MPLSsignaling within the BIER domain (e.g., Multicast Label DistributionProtocol (mLDP) signaling). Various example embodiments for supportingMPLS-based multicast over a BIER domain may be configured to supportstitching the MPLS datapath to the BIER domain based on identificationof P2MP LSPs within the BIER domain using BIER tree labels (BTLs) thatuniquely identify the P2MP LSPs (and, thus, are associated with theforwarding equivalence classes (FECs) for the P2MP LSPs) within the BIERdomain, respectively. Various example embodiments for supportingMPLS-based multicast over a BIER domain may be configured to supportassignment of a BTL for a P2MP LSP within the BIER domain, whichuniquely identifies the P2MP LSP within the BIER domain, by a controllerof the associated BIER domain (e.g., a Software Defined Networking (SDN)controller or other suitable type of controller), by a BIER borderrouter of the associated BIER domain (e.g., a BIER border router on theP2MP LSP, such as by a BIER border router that is an ingress point intothe BIER domain for multicast data traffic of the P2MP LSP), or thelike, as well as various combinations thereof. It will be appreciatedthat these and various other embodiments and potential advantages forsupporting stitching of P2MP LSPs via a BIER domain may be furtherunderstood by way of reference to the example communication system ofFIG. 1.

FIG. 1 depicts a communication system configured to support a P2MP LSPvia a BIER domain based on assignment of a label in the BIER domain thatuniquely identifies P2MP LSP within the BIER domain.

The communication system 100 includes a communication network (CN) 110that is configured to support multicasting of traffic to a multicasthost (MH) 120 from a multicast source (MS) 130.

The communication system 100 illustrates an arrangement in whichmulticast control traffic is propagated from right to left on the page(e.g., from the MH 120 toward the MS 130, via the CN 110, for enablingthe MH 120 to join and leave multicast services) and in which multicasttraffic is propagated from left to right on the page (e.g., from the MS130 toward the MH 120, via the CN 110, for enabling the MH 120 toreceive multicast data traffic).

The CN 110 is composed of an Interior Gateway Protocol (IGP) area(which, illustratively, may be IGP area 111-A or IGP area 111-S), a pairof MPLS domains 112-1 and 112-2 (collectively, MPLS domains 112), and aBIER domain 113. In at least some embodiments, the IGP area and the BIERdomain 113 are commensurate in scope as the entire IGP area isimplemented using BIER (illustrated in FIG. 1 using the IGP area 111-Aindicator). In at least some embodiments, the IGP area and the BIERdomain 113 are not commensurate in scope as only a portion of the IGParea is implemented using BIER (illustrated in FIG. 1 using the IGP area111-S indicator, which illustrates that the BIER domain 113 is actuallya BIER sub-domain that is only part of the IGP area 111-S). It will beappreciated that certain aspects of supporting multicast within the CN110 may vary depending on whether the BIER domain 113 forms all or partof the IGP area.

The CN 110 includes a set of MPLS routers 114-1-114-4 (collectively,MPLS routers 114) operating within the MPLS domains 112 and a set ofBIER routers 115 operating within the BIER domain 113. The set of BIERrouters 115 includes a set of BIER border routers (BBRs) 115-B1-115-B4(collectively, BBRs 115-B) and a BIER core router (BCR) 115-C. The MPLSrouters 114-1 and 114-2 (operating in the MPLS domain 112-1) are eachconnected to the BBRs 115-B1 and 115-B3 and the MPLS routers 114-3 and114-4 (operating in the MPLS domain 112-2) are each connected to theBBRs 115-B2 and 115-B4. The BBRs 115-B are each connected to the BCR115-C. The MH 120 is communicatively connected to MPLS router 114-4 viaan access network 121 and the MS 130 is communicatively connected to theMPLS router 114-2 via an access network 131.

The MPLS routers 114 are configured to facilitate communication betweenmulticast endpoints (e.g., MS 130 and MH 120) and the BBRs 115-B of theBIER domain 113. The MPLS routers 114 are configured to supportcommunication of multicast control traffic in the control trafficdirection based on multicast control protocols and communication ofmulticast data traffic in the data traffic direction based on multicastdata protocols.

The MPLS routers 114 are configured to support communications withmulticast endpoints, including multicast hosts (e.g., the MH 120) andmulticast sources (e.g., the MS 130). The MPLS routers 114 areconfigured to support multicast control communications with multicasthosts and multicast sources using various multicast control protocols(e.g., Label Distribution Protocol (LDP), Multicast LDP (mLDP), or thelike). For example, MPLS router 114-4 may receive multicast controlprotocol signaling from the MH 120 for enabling the MH 120 to join orleave a multicast group supported by MS 130 and, similarly, MS 130 mayreceive multicast control protocol signaling from the MPLS router 114-2for enabling the MH 120 to join or leave a multicast group supported byMS 130. The MPLS routers 114 are configured to support multicast datacommunications with multicast sources and multicast sources usingvarious data transport protocols (e.g., MPLS or the like). For example,MPLS router 114-2 may receive multicast data traffic from the MS 130 andMPLS router 114-4 may send multicast data traffic to the MH 120. TheMPLS routers 114 may be configured to support multicast control and datacommunications with multicast hosts and multicast sources based onvarious other types of protocols.

The MPLS routers 114 are configured to support communications with BBRs115-B. The MPLS routers 114 are configured to support multicast controlcommunications with BBRs 115-B using various multicast control protocols(e.g., LDP, mLDP, or the like). For example, MPLS router 114-4 may sendmulticast control protocol signaling received from the MH 120 (e.g., forenabling the MH 120 to join or leave a multicast group supported by MS130) to BBR 115-B2 or BBR 115-B4 and, similarly, MPLS router 114-2 mayreceive multicast control protocol signal intended for MS 130 (e.g., forenabling the MH 120 to join or leave a multicast group supported by MS130) from BBR 115-1 or BBR 115-3. The MPLS routers 114 are configured tosupport multicast data communications with BBRs 115-B using variousmulticast data protocols (e.g., MPLS or the like). For example, the MPLSrouter 114-2 may receive multicast data traffic from the MS 130 and sendthe multicast data to BBR 115-B1 or BBR 115-B3 and, similarly, MPLSrouter 114-4 may receive multicast data traffic from BBR 115-B2 or BBR115-B4 and send the multicast data to the MH 120. The communication ofmulticast data traffic between the MPLS routers 114 and the BBRs 115-Bmay be based on MPLS P2MP LSPs or other types of multicast datacommunication mechanisms. The MPLS routers 114 may be configured tosupport various other types of communications with BBRs 115-B.

The BIER routers 115 are configured to support BIER, an architecturethat, in general, provides multicast forwarding through a BIER domain(illustratively, BIER domain 113) without requiring intermediate routersto maintain multicast-related per-flow state and without requiring useof an explicit tree-building protocol. In the BIER architecture for aBIER domain, a multicast data packet enters the BIER domain at aBit-Forwarding Ingress Router (BFIR) and leaves the BIER domain at oneor more Bit-Forwarding Egress Routers (BFERs) based on use of a BIERpacket header that includes a Bit-String in which each bit representsone BFER (namely, the bits of the Bit-String are set in a mannerindicating the one or more BFERs to which the multicast data packet isto be provided). In general, in the BIER architecture for a BIER domain,the BIER domain may be identified by a unique BIER domain identifier andcan support multiple Bit-String Lengths. In the BIER architecture for aBIER domain, the BIER routers of the BIER domain also may be referred toherein as Bit Forwarding Routers (BFRs), which are routers thatparticipate in Bit Index Multipoint Forwarding. In the BIER architecturefor a BIER domain, each BFR of the BIER domain may be configured with aBFR-ID, a BFR-Prefix that uniquely identifies the BFR in the BIERdomain, a Bit String Length (BSL), a Sub-Domain (SD), a Set-Id (SI), andother parameters as defined in the BIER architecture documents. Variousother aspects of the BIER architecture will be understood from the BIERarchitecture documents.

The BBRs 115-B may be configured to operate as ingress border routers ofthe BIER domain 113 and as egress border routers of the BIER domain 113,where the mode of operation being used may vary depending on thelocations of the BBRs 115-B relative to the multicast hosts and themulticast sources, the type of communications being supported (e.g.,multicast control traffic versus multicast data traffic), or the like,as well as various combinations thereof.

Herein, unless indicated otherwise, the terms Bit-Forwarding IngressRouter (BFIR) and Bit-Forwarding Egress Router (BFER) are used inconjunction with handling of the multicast data traffic in the datatraffic direction from the MS 130 toward the MH 120. In general, theBFIR and the BFER support datapath stitching for forwarding of multicastdata traffic (e.g., MPLS packets) via the BIER domain 113. In general,the BFIR and the BFER may support datapath stitching for forwarding ofmulticast data traffic via the BIER domain 113 based on stitching of themulticast protocol used outside of the BIER domain 113 (e.g., MPLS) tothe BIER datapath within the BIER domain 113 (e.g., using BIER packetsbased on BIER packet headers) on the ingress and egress sides of theBIER domain 113, respectively. In general, a BFIR is the ingress borderrouter that supports datapath stitching for forwarding of multicast datatraffic based on receipt of the multicast data traffic based on MPLS,identification of a stitching forwarding entry, label handling (e.g.,based on the MPLS label for the P2MP LSP within the MPLS domain 112-1and based on the BTL of the associated P2MP LSP within the BIER domain113), and generation of a BIER packet including setting of the BIERheader fields. In general, a BFER is an egress border that is a leaf ofthe multicast tree and that supports datapath stitching for forwardingof multicast data traffic based on processing of the BIER header,removal of the multicast data traffic from the BIER packet, labelhandling (e.g., based on the BTL of the associated P2MP LSP within theBIER domain 113 and based on the MPLS label for the P2MP LSP within theMPLS domain 112-2), and forwarding of the multicast data traffic basedon MPLS. In other words, the BFIR and the BFER are the BBRs from themulticast data traffic point of view. For example, in the example ofFIG. 1, BBR 115-B3 would be a BFIR and BBR 115-B4 would be a BFER.

Herein, unless indicated otherwise, the terms Ingress BBR (IBBR) andEgress BBR (EBBR) are used in conjunction with handling of the multicastcontrol messages in the control traffic direction from the MH 120 towardthe MS 130. In general, an IBBR is an ingress boundary router between aMPLS domain (e.g., MPLS domain 112-2) and a BIER domain (e.g., BIERdomain 113) that receives MPLS signaling including MPLS signalinginformation, terminates the MPLS signaling, and forwards MPLS signalinginformation from the MPLS signaling within the BIER domain for enablingassignment of the BTL to identify the associated P2MP LSP within theBIER domain and to enable delivery of the MPLS signaling informationfrom the MPLS signaling to the multicast source (e.g., MS 130). Ingeneral, an EBBR is an egress boundary router between a BIER domain(e.g., BIER domain 113) and a MPLS domain (e.g., MPLS domain 112-1) thatreceives MPLS signaling information from the MPLS signaling terminatedby an IBBR and generates corresponding MPLS signaling including the MPLSsignaling information for delivery to the multicast source (e.g., MS130) via the MPLS domain. It will be appreciated that the MPLS signalinginformation may include a combination of a forwarding equivalence class(FEC) and an associated action (e.g., label mapping, label withdraw, orthe like) which may be denoted as <FEC, Action>. In other words, theIBBR and the EBBR are the BBRs from the control signaling point of view.For example, in the example of FIG. 1, BBR 115-B4 would be an IBBR andBBR 115-B3 would be an EBBR.

The BBRs 115-B, as discussed above, may be configured to operate asingress border routers and as egress border routers under variousconditions. As discussed above, a BFIR would be an EBBR of the controlplane traffic (e.g., BBR 115-B3) and a BFER would be an IBBR of thecontrol plane traffic (e.g., BBR 115-B4). Similarly, as discussed above,an IBBR would be a BFER of the multicast data traffic (e.g., BBR 115-B4)and an EBBR would be a BFIR of the multicast data traffic (e.g., BBR115-B3). In other words, each of the BBRs 115-B may be configured tooperate in multiple roles, for supporting control plane traffic and datatraffic, under various conditions.

The BBRs 115-B, given that the BIER domain 113 is an IGP area (whichcorresponds to the case of IGP area 111-A) or a portion of an IGP area(which corresponds to the case of IGP area 111-S), may be area borderrouters (ABRs) or autonomous system border routers (ASBRs) that areconnected to the edge network (e.g., MPLS routers 114) via anappropriate protocol (e.g., an IGP, a Border Gateway Protocol (BGP), orthe like), provider (P) routers that are selected to operate as BIERborder routers in the BIER domain 113, or the like, as well as variouscombinations thereof.

The BBRs 115-B, as discussed above, are configured to support datapathstitching for supporting forwarding of multicast data traffic of amulticast label switched path (e.g., MPLS packets of an LSP, such as aP2MP LSP) via the BIER domain 113. The stitching of the datapath forforwarding of multicast data traffic of a P2MP LSP via the BIER domain113 may be based on use of a BTL to uniquely identify the P2MP LSPwithin the BIER domain 113. For example, the BTL may be an MPLS labelthat uniquely identifies a P2MP LSP within the BIER domain 113. The BTLmay be assigned within the BIER domain 113 by a controller of the BIERdomain 113 (an embodiment of which is presented with respect to FIG. 2),by a BBR 115-B of the BIER domain 113 (embodiments of which arepresented with respect to FIG. 3 and FIG. 4), or the like, as well asvarious combinations thereof.

It will be appreciated that communication system 100, although primarilypresented as having a specific arrangement (e.g., specific types,numbers, and arrangements of domains, routers, multicast end devices,control plane protocols, datapath protocols, and the like), may havevarious other arrangements (e.g., other types, numbers, or arrangementsof domains, routers, multicast end devices, control plane protocols,datapath protocols, or the like, as well as various combinationsthereof).

FIG. 2 depicts a communication system for illustrating assignment of alabel to a P2MP LSP, for uniquely identifying the P2MP LSP within theBIER domain, by a controller of the BIER domain.

The communication system 200 of FIG. 2 is similar to the communicationsystem 100 of FIG. 1, with the exception that the BEIR domain 113 iscontrolled by a BIER domain controller 201 (although it will beappreciated that such a BIER domain controller also may be used withinthe context of communication system 100 of FIG. 1). The BIER domaincontroller 201 may be an SDN controller or other suitable type ofcontroller. In communication system 200, the BIER domain controller 201is responsible for assigning the BTL that uniquely identifies a P2MP LSPwithin the BIER domain 113. A description of a process for enabling theBIER domain controller 201 to assign the BTL that uniquely identifies anMPLS P2MP LSP within the BIER domain 113 follows.

The MPLS router (illustratively, MPLS router 114-4) associated with themulticast host (illustratively, MH 120) that is requesting to join themulticast group (S,G) of the P2MP LSP, sends MPLS signaling informationto an IBBR of the BIER domain (illustratively, IBBR 115-B4 of BIERdomain 113) using MPLS signaling in the MPLS domain (illustratively,MPLS domain 112-2). The MPLS signaling may be an mLDP control packet orother suitable control packet. The MPLS signaling information may be acombination of a FEC and an associated action (e.g., label mapping,label withdraw, or the like) which may be denoted as <FEC, Action> forthe P2MP LSP. It will be appreciated that the FEC may be a basic opaqueFEC (e.g., for a single IGP area) or may be a recursive opaque FEC(e.g., for seamless MPLS). In FIG. 2, the sending of the MPLS signalinginformation to the IBBR of the BIER domain is indicated by message 210.For example, the message 210 may include mLDP FEC (root, opaque<lspID1>,label1), mLDP FEC (root, opaque<lspID2>, label2), or the like.

The IBBR (illustratively, the BBR 115-B4) receives the mLDP signalingpacket including MPLS signaling information. The IBBR terminates theMPLS signaling and sends the MPLS signaling information of the MPLSsignaling to the BIER domain controller 201. The IBBR includes its ownBFR-Prefix and BFR-ID when sending the MPLS signaling information to theBIER domain controller 201. In FIG. 2, the sending of the MPLS signalinginformation and the BFR-Prefix of the IBBR from the IBBR to the BIERdomain controller 201 is indicated by message 220. For example, themessage 220 may include mLDP FEC (root, opaque<lspID1>) where message210 includes <mLDP FEC (root, opaque<lspID1>, label1)>, mLDP FEC (root,opaque<lspID2>) where message 210 includes <mLDP FEC (root,opaque<lspID2>, label2)>, or the like.

The BIER domain controller 201 receives the MPLS signaling informationand the BFR-Prefix of the IBBR from the IBBR.

The BIER domain controller 201 identifies the EBBR (illustratively, BBR115-B3) for which the MPLS signaling was intended. The BIER domaincontroller 201 may identify the EBBR based on the root address of theFEC from the MPLS signaling information. In the case of a basic opaque(Type 1) FEC, the root is the root of <root, opaque<id>>. In the case ofa recursive opaque FEC, the root is the outer root of <root,opaque<inner-root, opaque<id>>. The BIER domain controller 201 mayidentify the EBBR based on procedures defined in thedraft-ietf-bier-pim-signaling document.

The BIER domain controller 201 assigns a BTL for the FEC (and, thus, forthe associated P2MP LSP) from the MPLS signaling information. The BTLthat is assigned may be used to uniquely identify the associated P2MPLSP within the BIER domain 113 for supporting stitching of the P2MP LSPto the BIER datapath in the BIER domain 113. The BIER domain controller201 may assign the BTL from an overall label pool for the BIER domain113, from an <EBBR,SD> label pool associated with the EBBR for which theMPLS signaling was intended (e.g., where the BIER domain controller 201maintains a label pool per <EBBR,SD>, which may be used for betterscalability or for other purposes), or the like.

The BIER domain controller 201 tracks each of the IBBRs of the BIERdomain 113 that are receiving this FEC on the MPLS domain and would liketo join this specific P2MP LSP. The BIER domain controller 201 may trackthe IBBRs of the BIER domain 113 that are receiving this FEC on the MPLSdomain and would like to join this specific P2MP LSP by tracking theBFR-Prefixes and BFR-IDs of the IBBRs. As an example, each IBBR thatreceives the FEC and sends the FEC (along with its BFR-Prefix andBFR-ID) to the BIER domain controller 201 will be tracked by the BIERdomain controller 201. This tracking enables the EBBR to build thecorrect BIER header and set the bits (in the BIER header) for all theIBBRs that are interested in the traffic from this specific P2MP LSP.

The BIER domain controller 201 updates the relevant BBRs of the BIERdomain with the BTL identifying the P2MP LSP within the BIER domain 113.The relevant BBRs may include the IBBRs and the EBBR that are interestedin the P2MP LSP. For example, the relevant EBBR may be the EBBR that isclosest to the root node of the P2MP LSP (illustratively, BBR 115-B3)and the relevant IBBRs may include any IBBRs that have terminated theMPLS domain and extracted the FEC to the BIER domain controller 201 forthe P2MP LSP (illustratively, BBR 115-B4). The BIER domain controller201 updates the relevant BBRs with the BTL identifying the P2MP LSP bysending the MPLS signaling information and the BTL identifying the P2MPLSP to the relevant BBRs. The sending of the MPLS signaling informationand the BTL identifying the P2MP LSP may be denoted as <EBBR(BFR-Prefix), SD> (BTL), <IBBR (BFR-Prefix), FEC, Action>>. The BIERdomain controller 201 may send the MPLS signaling information and theBTL identifying the P2MP LSP to the relevant BBRs via downloading intothe relevant BBRs. In FIG. 2, the sending of the MPLS signalinginformation and the BTL identifying the P2MP LSP from the BIER domaincontroller 201 to relevant BBRs is indicated by messages 230. Forexample, the messages 230 may include [<EBBR BFR-Prefix, SD> (BTL-1),<IBBR BFR-Prefix, mLDP FEC (root, opaque<lspID1>, Action>] where message210 includes <mLDP FEC (root, opaque<lspID1>, label1)>, [<EBBR Prefix,SD> (BTL-2), <IBBR BFR-Prefix, mLDP FEC (root, opaque<lspID2>, Action>]where message 210 includes <mLDP FEC (root, opaque<lspID2>, label2)>, orthe like.

The relevant EBBR (illustratively, BBR 115-B3) receives the MPLSsignaling information and the BDT identifying the P2MP LSP from the BIERdomain controller 201. The relevant EBBR, based on the MPLS signalinginformation, assigns a new outgoing label toward the root node(illustratively, MPLS router 114-2) for MPLS signaling within the MPLSdomain (illustratively, MPLS domain 112-1). The relevant EBBRreconstitutes MPLS signaling and sends the MPLS signaling information tothe root node using MPLS signaling. In FIG. 2, the sending of the MPLSsignaling information from the relevant EBBR to the root node isindicated by message 240. For example, the message 240 may include <mLDPFEC (root, opaque<lspID1>, label3)> where message 210 includes <mLDP FEC(root, opaque<lspID1>, label1)>, <mLDP FEC (root, opaque<lspID1>,label4)> where message 210 includes <mLDP FEC (root, opaque<lspID2>,label2)>, or the like.

The relevant EBBR (illustratively, BBR 115-B3) receives the MPLSsignaling information and the BDT identifying the P2MP LSP from the BIERdomain controller 201. The relevant EBBR (illustratively, BBR 115-B3),based on the IBBR BFR-Prefix of the IBBR (illustratively, BBR 115-B4)which received the MPLS signaling information for the P2MP LSP,configures a stitched label forwarding entry on the relevant EBBR forthe IBBR indicated by the IBBR BFR-Prefix. The stitched label forwardingentry is configured to stitch the incoming MPLS domain label for theP2MP LSP to the outgoing BTL which was uniquely assigned for the P2MPLSP by the BIER domain controller 201, with the outgoing interfaces(OIFs) being each of the IBBRs interested in the P2MP LSP (at leastincluding the IBBR indicated by the IBBR BFR-Prefix received from theBIER domain controller 201). On the dataplane, as discussed furtherbelow, the relevant EBBR will use the BFR-Prefixes, of the IBBRsinterested in the P2MP LSP in the corresponding SD, as the OIFs in orderto find the corresponding BIER header bit index for each IBBR in its OIFlist.

The relevant IBBR (illustratively, BBR 115-B4) receives the MPLSsignaling information and the BDT identifying the P2MP LSP from the BIERdomain controller 201. The relevant IBBR (illustratively, BBR 115-B4),based on the EBBR BFR-Prefix of the relevant EBBR (illustratively, BBR115-B3) that is received, configures a stitched label forwarding entryon the relevant IBBR for the EBBR indicated by the EBBR BFR-Prefix. Thestitched label forwarding entry is configured to stitch the incomingEBBR BFR-Prefix (BTL) for the P2MP LSP to the outgoing MPLS domain labelfor the P2MP LSP in the corresponding SD. On the dataplane, as discussedfurther below, the relevant IBBR will (1) use the BIER header todetermine that the BIER payload is an MPLS packet and (2) remove theBIER header and use the BTL pushed by the EBBR to do a lookup in the ILMfor the EBBR BFR-Prefix (BTL) for determining handling of the packet inthe MPLS domain (illustratively, MPLS domain 112-2).

It will be appreciated that, while primarily presented in FIG. 2 withinthe context of handling of a specific type of action for the multicasttree (namely, a label mapping action in which the MPLS router 114 isjoining the multicast tree), various embodiments of FIG. 2 may beadapted for use in handling other types of actions (e.g., a labelwithdraw action in which the MPLS router 114 is leaving the multicasttree or the like).

It will be appreciated that, while primarily presented in FIG. 2 withinthe context of embodiments in which the multicast datapath is providedusing MPLS and the multicast control signaling is based on mLDP, variousembodiments may adapted for use with other multicast datapath protocols,other multicast control signaling protocols, or the like, as well asvarious combinations thereof.

FIG. 3 depicts a communication system for illustrating assignment of alabel to a P2MP LSP, for uniquely identifying the P2MP LSP within theBIER domain, by a BBR of the BIER domain.

The communication system 300 of FIG. 3 is similar to the communicationsystem 100 of FIG. 1, with the exception that the BEIR domain 113 iscontrolled by a BIER domain controller 301 (although it will beappreciated that such a BIER domain controller also may be used withinthe context of communication system 100 of FIG. 1). The BIER domaincontroller 301 may be an SDN controller or other suitable type ofcontroller. In communication system 300, an EBBR (illustratively, BBR115-B3) is responsible for assigning the BTL that uniquely identifies aP2MP LSP within the BIER domain 113 and the BIER domain controller 301is responsible for distributing the BTL that uniquely identifies theP2MP LSP within the BIER domain 113. A description of a process forenabling the EBBR to assign the BTL that uniquely identifies a P2MP LSPwithin the BIER domain 113 and for enabling the BIER domain controller301 to distribute the BTL that uniquely identifies the P2MP LSP withinthe BIER domain 113 follows. The MPLS router (illustratively, MPLSrouter 114-4) associated with the multicast host (illustratively, MH120) that is requesting to join the multicast group (S,G) of the P2MPLSP, sends MPLS signaling information to an IBBR of the BIER domain(illustratively, IBBR 115-B4 of BIER domain 113) using MPLS signaling inthe MPLS domain (illustratively, MPLS domain 112-2). The MPLS signalingmay be an mLDP signaling packet or other suitable signaling packet. TheMPLS signaling information may be a combination of a FEC and anassociated action (e.g., label mapping, label withdraw, or the like)which may be denoted as <FEC, Action> for the P2MP LSP. It will beappreciated that the FEC may be a basic opaque FEC (e.g., for a singleIGP area) or may be a recursive opaque FEC (e.g., for seamless MPLS). InFIG. 3, the sending of the MPLS signaling information to the IBBR of theBIER domain is indicated by message 310. For example, the message 310may be an mLDP label mapping message including mLDP FEC (root,opaque<lspID1>, label1), mLDP FEC (root, opaque<lspID2>, label2), or thelike.

The IBBR (illustratively, the BBR 115-B4) receives the MPLS signalingincluding MPLS signaling information. The IBBR terminates the MPLSsignaling, identifies the EBBR (illustratively, BBR 115-B3) for whichthe MPLS signaling was intended, and sends the MPLS signalinginformation of the MPLS signaling to the EBBR for which the MPLSsignaling was intended.

The IBBR identifies the EBBR (illustratively, BBR 115-B3) for which theMPLS signaling was intended. The IBBR may identify the EBBR based on theroot address of the FEC from the MPLS signaling information. In the caseof a basic opaque (Type 1) FEC, the root is the root of <root,opaque<id>>. In the case of a recursive opaque FEC, the root is theouter root of <root, opaque<inner-root, opaque<id>>. The IBBR mayidentify the EBBR based on procedures defined in thedraft-ietf-bier-pim-signaling document.

The IBBR sends the MPLS signaling information of the MPLS signaling tothe EBBR for which the MPLS signaling was intended using BIER signaling.The IBBR sends the MPLS signaling information of the MPLS signaling tothe EBBR for which the MPLS signaling was intended by encapsulating theMPLS signaling information of the MPLS signaling within a BIER packet,setting the BIER header to indicate routing of the BIER packet to theEBBR for which the MPLS signaling was intended (e.g., by setting theBIER header bit corresponding to the EBBR for which the MPLS signalingwas intended), and forwarding the BIER packet into the BIER domain fordelivery to the EBBR for which the MPLS signaling was intended. The MPLSsignaling information may be encapsulated within the BIER packet byencapsulating the MPLS signaling packet (including the MPLS signalinginformation) within the BIER packet or by only encapsulating the MPLSsignaling information (rather than the entire MPLS signaling packet)within the BIER packet. It is noted that, here, the BIER domain does notcreate mLDP adjacency between the two disjoint mLDP domains; rather, theBIER domain merely uses the mLDP packet for signaling purposes. In FIG.3, the sending of the MPLS signaling information from the IBBR to theEBBR is indicated by message 320. For example, the message 320 mayinclude mLDP FEC (root, opaque<lspID1>) where message 310 includes <mLDPFEC (root, opaque<lspID1>, label1)>, mLDP FEC (root, opaque<lspID2>)where message 310 includes <mLDP FEC (root, opaque<lspID2>, label2)>, orthe like.

The EBBR receives the BIER packet including the MPLS signalinginformation from the IBBR. The EBBR removes the MPLS signalinginformation from the BIER packet and processes the MPLS signalinginformation.

The EBBR, based on a determination that this is the first IBBR that hasforwarded the FEC to the EBBR, assigns a BTL for the FEC (and, thus, forthe associated P2MP LSP) from the MPLS signaling information. The BTLthat is assigned may be used to uniquely identify the associated P2MPLSP within the BIER domain 113 for supporting stitching of the P2MP LSPto the BIER datapath in the BIER domain 113. The EBBR may assign the BTLfrom an overall label pool for the BIER domain 113, from an <EBBR,SD>label pool associated with the EBBR (e.g., where the BIER domaincontroller 301 maintains a label pool per <EBBR,SD>, which may be usedfor better scalability or for other purposes, and distributes theper-EBBR label pools to the EBBRs, respectively), or the like. It isnoted that the EBBR, based on a determination that this is not the firstIBBR that has forwarded the FEC to the EBBR (but, rather, is asubsequent IBBR interested in the P2MP LSP), will add the IBBRBFR-Prefix to the OIF list of the FEC (since the EBBR will have alreadyassigned the BTL for the FEC, as described above, when the FEC wasreceived from the first IBBR interested in the P2MP LSP).

The EBBR sends the MPLS signaling information and the BTL identifyingthe P2MP LSP to the BIER domain controller 301 such that the BIER domaincontroller 301 may further distribute the MPLS signaling information andthe BTL identifying the P2MP LSP. For example, the EBBR may create amessage <<EBBR, SD> BTL, <IBBR, <FEC, Action>>, where EBBR and IBBR arethe BFR-Prefixes and BFR-IDs of the EBBR and the IBBR, respectively. InFIG. 3, the sending of the MPLS signaling information and the BTLidentifying the P2MP LSP from the EBBR to the BIER domain controller 301is indicated by message 330. For example, the message 330 may include[<EBBR BFR-Prefix, BFR-ID, SD> (BTL-1), <IBBR BFR-Prefix, BFR-ID, mLDPFEC (root, opaque<lspID1>, Action>] where message 310 includes <mLDP FEC(root, opaque<lspID1>, label1)>, [<EBBR BFR-Prefix, BFR-ID, SD> (BTL-2),<IBBR BFR-Prefix, BFR-ID, mLDP FEC (root, opaque<lspID2>>] where message310 includes <mLDP FEC (root, opaque<lspID2>, label2)>, or the like.

The BIER domain controller 301 receives the MPLS signaling informationand the BTL identifying the P2MP LSP from the EBBR (illustratively, BBR115-B3). The BIER domain controller 301 sends the MPLS signalinginformation and the BTL identifying the P2MP LSP to IBBRs of the BIERdomain 113, which may include all of the IBBRs of the BIER domain 113 orIBBRs of the BIER domain 113 that are relevant to the P2MP LSP. Therelevant IBBRs may include any IBBRs that have terminated the MPLSdomain and extracted the FEC to the BIER domain controller 301 for theP2MP LSP (illustratively, BBR 115-B4). The sending of the MPLS signalinginformation and the BTL identifying the P2MP LSP may be denoted as <EBBR(BFR-Prefix, BFR-ID), SD> (BTL), <IBBR (BFR-Prefix, BFR-ID), FEC,Action>>. The BIER domain controller 301 may send the MPLS signalinginformation and the BTL identifying the P2MP LSP to IBBRs viadownloading into the IBBRs. In FIG. 3, the sending of the MPLS signalinginformation and the BTL identifying the P2MP LSP from the BIER domaincontroller 301 to relevant IBBRs is indicated by message 340. Forexample, the message 340 may include [<EBBR BFR-Prefix, BFR-ID, SD>(BTL-1), <IBBR BFR-Prefix, BFR-ID, mLDP FEC (root, opaque<lspID1>,Action>] where message 310 includes <mLDP FEC (root, opaque<lspID1>,label1)>, [<EBBR BFR-Prefix, SD> (BTL-2), <IBBR BFR-Prefix, mLDP FEC(root, opaque<lspID2>>] where message 310 includes <mLDP FEC (root,opaque<lspID2>, label2)>, or the like.

The relevant IBBR (illustratively, BBR 115-B4) receives the MPLSsignaling information and the BDT identifying the P2MP LSP from the BIERdomain controller 301. The relevant IBBR (illustratively, BBR 115-B4),based on the EBBR BFR-Prefix of the relevant EBBR (illustratively, BBR115-B3) that is received, configures a stitched label forwarding entryon the relevant IBBR for the EBBR indicated by the EBBR BFR-Prefix. Thestitched label forwarding entry is configured to stitch the incomingEBBR BFR-Prefix (BTL) for the P2MP LSP to the outgoing MPLS domain labelfor the P2MP LSP. On the dataplane, as discussed further below, therelevant IBBR will look at the BIER header protocol and, if the BIERheader protocol is MPLS, will remove the BIER header and use the BTLunder the BIER header to do a lookup in ILM for the EBBR BFR-Prefix(BTL) for determining handling of the packet in the MPLS domain(illustratively, MPLS domain 112-2).

The EBBR (illustratively, BBR 115-B3), in addition to assigning the BTLfor the FEC from the MPLS signaling information, uses the IBBRBFR-Prefix, of the IBBR (illustratively, BBR 115-B4) which received theMPLS signaling information for the P2MP LSP, to configure a new stitchedlabel forwarding entry on the EBBR, where the stitched label forwardingentry is configured to stitch the incoming MPLS domain label for theP2MP LSP to the outgoing BTL for the P2MP LSP, with the outputinterfaces (OIFs) being each of the IBBRs interested in the P2MP LSP. Onthe dataplane, as discussed further below, the EBBR will use theBFR-Prefixes of the IBBRs interested in the P2MP LSP as the OIFs inorder to find the corresponding BIER header bit index for each IBBR inits OIF list.

The EBBR (illustratively, BBR 115-B3), in addition to assigning the BTLfor the FEC from the MPLS signaling information, assigns a new outgoinglabel toward the root node (illustratively, MPLS router 114-2) for MPLSsignaling within the MPLS domain (illustratively, MPLS domain 112-1).The EBBR reconstitutes MPLS signaling and sends the MPLS signalinginformation to the root node using MPLS signaling. In FIG. 3, thesending of the MPLS signaling information from the EBBR to the root nodeis indicated by message 350. For example, the message 350 may include<mLDP FEC (root, opaque<lspID1>, label3)> where message 310 includes<mLDP FEC (root, opaque<lspID1>, label1)>, <mLDP FEC (root,opaque<lspID1>, label4)> where message 310 includes <mLDP FEC (root,opaque<lspID2>, label2)>, or the like.

It will be appreciated that, while primarily presented in FIG. 3 withinthe context of handling of a specific type of action for the multicasttree (namely, a label mapping action in which the MPLS router 114 isjoining the multicast tree), various embodiments of FIG. 3 may beadapted for use in handling other types of actions (e.g., a labelwithdraw action in which the MPLS router 114 is leaving the multicasttree or the like).

It will be appreciated that, while primarily presented in FIG. 3 withinthe context of embodiments in which the multicast datapath is providedusing MPLS and the multicast control signaling is based on mLDP, variousembodiments may adapted for use with other multicast datapath protocols,other multicast control signaling protocols, or the like, as well asvarious combinations thereof.

FIG. 4 depicts a communication system for illustrating assignment of alabel to a P2MP LSP, for uniquely identifying the P2MP LSP within theBIER domain, by a BBR of the BIER domain.

The communication system 400 of FIG. 4 is similar to the communicationsystem 100 of FIG. 1. It will be appreciated that, although omitted forpurposes of clarity, the communication system 400 may include a BIERdomain controller configured to control elements of the BIER domain 113(e.g., an SDN controller or other suitable type of controller. Incommunication system 400, an EBBR (illustratively, BBR 115-B3) isresponsible for assigning the BTL that uniquely identifies a P2MP LSPwithin the BIER domain 113 and for distributing the BTL that uniquelyidentifies the P2MP LSP within the BIER domain 113. A description of aprocess for enabling the EBBR to assign the BTL that uniquely identifiesa P2MP LSP within the BIER domain 113 and for enabling the EBBR todistribute the BTL that uniquely identifies the P2MP LSP within the BIERdomain 113 follows.

The MPLS router (illustratively, MPLS router 114-4) associated with themulticast host (illustratively, MH 120) that is requesting to join themulticast group (S,G) of the P2MP LSP, sends MPLS signaling informationto an IBBR of the BIER domain (illustratively, IBBR 115-B4 of BIERdomain 113) using MPLS signaling in the MPLS domain (illustratively,MPLS domain 112-2). The MPLS signaling may be mLDP signaling packet orother suitable signaling packet. The MPLS signaling information may be acombination of a FEC and an associated action (e.g., label mapping,label withdraw, or the like) which may be denoted as <FEC, Action> forthe P2MP LSP. It will be appreciated that the FEC may be a basic opaqueFEC (e.g., for a single IGP area) or may be a recursive opaque FEC(e.g., for seamless MPLS). In FIG. 4, the sending of the MPLS signalinginformation to the IBBR of the BIER domain is indicated by message 410.For example, the message 310 may include mLDP FEC (root, opaque<lspID1>,label1), mLDP FEC (root, opaque<lspID2>, label2), or the like.

The IBBR (illustratively, the BBR 115-B4) receives the MPLS signalingincluding MPLS signaling information. The IBBR terminates the MPLSsignaling, identifies the EBBR (illustratively, BBR 115-B3) for whichthe MPLS signaling was intended, and sends the MPLS signalinginformation of the MPLS signaling to the EBBR for which the MPLSsignaling was intended.

The IBBR identifies the EBBR (illustratively, BBR 115-B3) for which theMPLS signaling was intended. The IBBR may identify the EBBR based on theroot address of the FEC from the MPLS signaling information. In the caseof a basic opaque (Type 1) FEC, the root is the root of <root,opaque<id>>. In the case of a recursive opaque FEC, the root is theouter root of <root, opaque<inner-root, opaque<id>>. The IBBR mayidentify the EBBR based on procedures defined in thedraft-ietf-bier-pim-signaling document.

The IBBR sends the MPLS signaling information of the MPLS signaling tothe EBBR for which the MPLS signaling was intended using BIER signaling.The IBBR sends the MPLS signaling information of the MPLS signaling tothe EBBR for which the MPLS signaling was intended by encapsulating theMPLS signaling information of the MPLS signaling within a BIER packet,setting the BIER header to indicate routing of the BIER packet to theEBBR for which the MPLS signaling was intended (e.g., by setting theBIER header bit corresponding to the EBBR for which the MPLS signalingwas intended), and forwarding the BIER packet into the BIER domain fordelivery to the EBBR for which the MPLS signaling was intended. The MPLSsignaling information may be encapsulated within the BIER packet byencapsulating the MPLS signaling packet (including the MPLS signalinginformation) within the BIER packet or by only encapsulating the MPLSsignaling information (rather than the entire MPLS signaling packet)within the BIER packet. It is noted that, here, the BIER domain does notcreate mLDP adjacency between the two disjoint mLDP domains; rather, theBIER domain merely uses the mLDP packet for signaling purposes. In FIG.4, the sending of the MPLS signaling information from the IBBR to theEBBR is indicated by message 420. For example, the message 420 mayinclude mLDP FEC (root, opaque<lspID1>) where message 410 includes <mLDPFEC (root, opaque<lspID1>, label1)>, mLDP FEC (root, opaque<lspID2>)where message 410 includes <mLDP FEC (root, opaque<lspID2>, label2)>, orthe like.

The EBBR receives the BIER packet including the MPLS signalinginformation from the IBBR. The EBBR removes the MPLS signalinginformation from the BIER packet and processes the MPLS signalinginformation.

The EBBR, based on a determination that this is the first IBBR that hasforwarded the FEC to the EBBR, assigns a BTL for the FEC (and, thus, forthe associated P2MP LSP) from the MPLS signaling information. The BTLthat is assigned may be used to uniquely identify the associated P2MPLSP within the BIER domain 113 for supporting stitching of the P2MP LSPto the BIER datapath in the BIER domain 113. The EBBR may assign the BTLfrom an overall label pool for the BIER domain 113, from an <EBBR,SD>label pool associated with the EBBR (e.g., where the BIER domaincontroller 301 maintains a label pool per <EBBR,SD>, which may be usedfor better scalability or for other purposes, and distributes theper-EBBR label pools to the EBBRs, respectively), or the like. It isnoted that the EBBR, based on a determination that this is not the firstIBBR that has forwarded the FEC to the EBBR (but, rather, is asubsequent IBBR interested in the P2MP LSP), will add the IBBRBFR-Prefix to the OIF list of the FEC (since the EBBR will have alreadyassigned the BTL for the FEC, as described above, when the FEC wasreceived from the first IBBR interested in the P2MP LSP).

The EBBR sends the MPLS signaling information and the BTL identifyingthe P2MP LSP to the IBBR from which the MPLS signaling information wasreceived (namely, BBR 115-B4). The EBBR may send the MPLS signalinginformation and the BTL identifying the P2MP LSP to the IBBR from whichthe MPLS signaling information was received based on aMultiprotocol-Border Gateway Protocol (MP-BGP) adjacency to the IBBRfrom which the MPLS signaling information was received (e.g., based on aP-Multicast Service Interface (PMSI) Tunnel Attribute (PTA) and NetworkLayer Reachability Information (NLRI)). The EBBR may send the MPLSsignaling information and the BTL identifying the P2MP LSP to the IBBRfrom which the MPLS signaling information was received based on a BGPMulticast Virtual Private Network (MVPN). The EBBR may send the MPLSsignaling information and the BTL identifying the P2MP LSP to the IBBRfrom which the MPLS signaling information was received based on SegmentRouting-Traffic Engineering (SR-TE). In FIG. 4, the sending of the MPLSsignaling information and the BTL identifying the P2MP LSP from the EBBRto the IBBR from which the MPLS signaling information was received isindicated by message 430. For example, the message 430 may include[<EBBR BFR-Prefix, SD> (BTL-1), <IBBR BFR-Prefix, mLDP FEC (root,opaque<lspID1>>] where message 410 includes <mLDP FEC (root,opaque<lspID1>, label1)>, [<EBBR BFR-Prefix, SD> (BTL-2), <IBBRBFR-Prefix, mLDP FEC (root, opaque<lspID2>>] where message 410 includes<mLDP FEC (root, opaque<lspID2>, label2)>, or the like.

The relevant IBBR (illustratively, BBR 115-B4) receives the MPLSsignaling information and the BDT identifying the P2MP LSP from theEBBR. The relevant IBBR (illustratively, BBR 115-B4), based on the EBBRBFR-Prefix of the relevant EBBR (illustratively, BBR 115-B3) that isreceived, configures a stitched label forwarding entry on the relevantIBBR for the EBBR indicated by the EBBR BFR-Prefix. The stitched labelforwarding entry is configured to stitch the incoming EBBR BFR-Prefix(BTL) for the P2MP LSP to the outgoing MPLS domain label for the P2MPLSP. On the dataplane, as discussed further below, the relevant IBBRwill look at the BIER header protocol and, if the BIER header protocolis MPLS, will perform a lookup in the ILM for the EBBR BFR-Prefix (BTL)for determining handling of the packet in the MPLS domain(illustratively, MPLS domain 112-2).

The EBBR (illustratively, BBR 115-B3), in addition to assigning the BTLfor the FEC from the MPLS signaling information, uses the IBBRBFR-Prefix, of the IBBR (illustratively, BBR 115-B4) which received theMPLS signaling information for the P2MP LSP, to configure a new stitchedlabel forwarding entry on the EBBR, where the stitched label forwardingentry is configured to stitch the incoming MPLS domain label for theP2MP LSP to the outgoing BTL for the P2MP LSP, with the outputinterfaces (OIFs) being each of the IBBRs interested in the P2MP LSP. Onthe dataplane, as discussed further below, the EBBR will use theBFR-Prefixes of the IBBRs interested in the P2MP LSP as the OIFs inorder to find the corresponding BIER header bit index for each IBBR inits OIF list.

The EBBR (illustratively, BBR 115-B3), in addition to assigning the BTLfor the FEC from the MPLS signaling information, assigns a new outgoinglabel toward the root node (illustratively, MPLS router 114-2) for MPLSsignaling within the MPLS domain (illustratively, MPLS domain 112-1).The EBBR reconstitutes MPLS signaling and sends the MPLS signalinginformation to the root node using MPLS signaling. In FIG. 4, thesending of the MPLS signaling information from the EBBR to the root nodeis indicated by message 440. For example, the message 440 may include<mLDP FEC (root, opaque<lspID1>, label3)> where message 410 includes<mLDP FEC (root, opaque<lspID1>, label1)>, <mLDP FEC (root,opaque<lspID1>, label4)> where message 410 includes <mLDP FEC (root,opaque<lspID2>, label2)>, or the like.

It will be appreciated that, while primarily presented in FIG. 4 withinthe context of handling of a specific type of action for the multicasttree (namely, a label mapping action in which the MPLS router 114 isjoining the multicast tree), various embodiments of FIG. 4 may beadapted for use in handling other types of actions (e.g., a labelwithdraw action in which the MPLS router 114 is leaving the multicasttree or the like).

It will be appreciated that, while primarily presented in FIG. 4 withinthe context of embodiments in which the multicast datapath is providedusing MPLS and the multicast control signaling is based on mLDP, variousembodiments may adapted for use with other multicast datapath protocols,other multicast control signaling protocols, or the like, as well asvarious combinations thereof.

FIG. 5 depicts a communication system for illustrating transport of MPLSpackets of a P2MP LSP across a BIER domain based on assignment of alabel to the P2MP LSP for uniquely identifying the P2MP LSP within theBIER domain.

The communication system 500 of FIG. 5 is similar to the communicationsystem 100 of FIG. 1. In communication system 500, a BTL has beenassigned to a P2MP LSP for uniquely identifying the P2MP LSP within theBIER domain 113. A description of a process for routing a multicastpacket via the P2MP LSP across the BIER domain 113 based on the BTLassigned to the P2MP LSP (e.g., assigned as presented with respect toany of FIGS. 2-4) follows. In this example, for purposes of clarity, itis assumed that only the MH 120 is part of the multicast group.

The multicast source (illustratively, MS 130) sends an MPLS packet to amulticast group (e.g., multicast group (S, G)) that includes a multicasthost (illustratively, MH 120). It will be appreciated that the multicastgroup may include other multicast hosts; however, for purposes ofclarity, routing of the MPLS packet to MH 120 is presented. Themulticast source provides the MPLS packet to its associated MPLS router(illustratively, MPLS router 114-2 communicatively connected to MS 130via access network 131).

The MPLS router (illustratively, MPLS router 114-2) associated with themulticast source (illustratively, MS 130) receives the MPLS packet fromthe multicast source and sends the MPLS packet to the associated BFIR ofthe multicast tree for the multicast group (illustratively, BBR 115-B3)via the associated MPLS domain (illustratively, MPLS domain 112-1). TheMPLS packet is routed via the MPLS domain based on an MPLS label for theP2MP LSP within the MPLS domain.

The BFIR of the multicast tree for the multicast group (illustratively,BBR 115-B3) receives the MPLS packet via the associated MPLS domain(illustratively, MPLS domain 112-1).

The BFIR performs a lookup based on the MPLS label of the MPLS packet toidentify the BTL for the P2MP LSP within the BIER domain. The BFIR mayperform the lookup to identify the BTL for the P2MP LSP within the BIERdomain in the ILM table of the BFIR.

The BFIR replaces the MPLS label for the P2MP LSP within the MPLS domainwith the BTL for the P2MP LSP within the BIER domain (e.g., by swappingthe MPLS label with the BTL, by popping the MPLS label and pushing theBTL, or the like).

The BFIR encapsulates the MPLS packet within a BIER header to form aBIER packet and forwards the BIER packet into the BIER domain. The BFIRidentifies IBBRs of the BIER domain that belong to the multicast groupand, thus, are interested in the P2MP LSP for the multicast group. TheBFIR may identify IBBRs of the BIER domain that belong to the multicastgroup by checking the outgoing interface list of the BTL for the P2MPLSP (which includes a list of the BFR-Prefixes and BFR-IDs of the IBBRsthat belong to the multicast group for the P2MP LSP). The BFIR sets theBIER Bit Index of the BIER header in a manner that indicates each of theBBRs of the BIER domain identified as belonging to the multicast group.The BFIR sets the BIER Header Protocol field in a manner that indicatesthe protocol of the packet being transported by the BIER packet in theBIER domain (e.g., BIERHeader.Proto=MPLS since the packet is an MPLSpacket entering the BIER domain 113 from MPLS domain 112-1). The BFIRmay set other fields of the BIER header. The BFIR forwards the BIERpacket into the BIER domain within the corresponding SD for transportingthe MPLS packet across the SD based on stitching of the MPLS P2MP LSPand the BIER datapath.

The BIER domain uses BIER forwarding procedures (e.g., based on RFC8279) to provide the BIER packet to each of the IBBRs that belong to themulticast group (illustratively, BBR 115-B4, which is the IBBR for themulticast group).

The IBBRs of the BIER domain that correspond to the same SD and that areinterested in the P2MP LSP (illustratively, BBR 115-B4 which is the EBBRfor MH 120) receive the BIER packet. The IBBR that is identified is theBFER of the BIER datapath for the P2MP LSP. The BFER that receives theBIER packet checks the protocol of the BIER header (in this example,BIERHeader.Proto=MPLS). The BFER that receives the BIER packet performsa lookup based on the BFR-ID of the BIER packet to identify the EBBRlabel pool base for the BIER packet. The BFER that receives the BIERpacket removes the BIER header of the BIER packet and performs a lookupbased on the EBBR BFR-Prefix (BTL) to identify the MPLS label for theP2MP LSP within the MPLS domain (illustratively, MPLS domain 112-2). TheBFER may perform the lookup to identify the MPLS label for the P2MP LSPwithin the MPLS domain in the ILM table (e.g., the ILM table for theEBBR BFR-Prefix (BTL)) of the BFER.

The BFER replaces the BTL for the P2MP LSP within the BIER domain withthe MPLS label for the P2MP LSP within the MPLS domain (e.g., byswapping the BTL with the MPLS label, by popping the BTL and pushing theMPLS label, or the like).

The BFER forwards the MPLS packet to each of the MPLS OIFs on the BFERsuch that the MPLS packet is delivered to each of the MPLS routersserving multicast hosts that belong to the multicast group(illustratively, for delivery to MPLS router 114-4 that serves MH 120).

The MPLS router that serves the multicast host belonging to themulticast group (illustratively, MPLS router 114-4 that serves MH 120)receives the MPLS and forwards the MPLS packet toward the multicast host(illustratively, toward MH 120 via associate access network 121).

It will be appreciated that, while primarily presented in FIG. 5 withinthe context of embodiments in which the multicast datapath is providedusing MPLS, various embodiments may adapted for use with other multicastdatapath protocols.

FIG. 6 depicts an example embodiment of a method for use by an IBBR forsupporting assignment of a label to a P2MP LSP within a BIER domain foruniquely identifying the P2MP LSP within the BIER domain. It will beappreciated that, although primarily presented herein as being performedserially, at least a portion of the functions of method 600 may beperformed contemporaneously or in a different order than as presented inFIG. 6. At block 601, method 600 begins. At block 610, receive, by a BBRof a BIER domain from an MPLS domain, MPLS signaling informationassociated with a P2MP LSP. At block 620, send, by the BBR toward adevice configured to assign a BTL identifying the P2MP LSP within theBIER domain, the MPLS signaling information associated with the P2MPLSP. At block 699, method 600 ends. It will be appreciated that variousother functions presented herein as being supported by IBBRs (e.g., aspresented in FIGS. 1-5) may be performed within the context of method600 of FIG. 6 or using one or more other methods which may be performedin conjunction with or independent of method 600 of FIG. 6.

FIG. 7 depicts an example embodiment of a method for use by a BTLassigning node for supporting assignment of a label to a P2MP LSP withina BIER domain for uniquely identifying the P2MP LSP within the BIERdomain. It will be appreciated that, although primarily presented hereinas being performed serially, at least a portion of the functions ofmethod 700 may be performed contemporaneously or in a different orderthan as presented in FIG. 7. At block 701, method 700 begins. At block710, receive, by a device associated with a BIER domain, MPLS signalinginformation associated with a P2MP LSP. At block 720, assign, by thedevice based on the MPLS signaling information associated with the P2MPLSP, a BTL identifying the P2MP LSP within the BIER domain. At block799, method 700 ends. It will be appreciated that various otherfunctions presented herein as being supported by BDT assigning entities(e.g., as presented in FIGS. 1-5) may be performed within the context ofmethod 700 of FIG. 7 or using one or more other methods which may beperformed in conjunction with or independent of method 700 of FIG. 7.

FIG. 8 depicts an example embodiment of a method for use by an EBBR forsupporting assignment of a label to a P2MP LSP within a BIER domain foruniquely identifying the P2MP LSP within the BIER domain. It will beappreciated that, although primarily presented herein as being performedserially, at least a portion of the functions of method 800 may beperformed contemporaneously or in a different order than as presented inFIG. 8. At block 801, method 800 begins. At block 810, obtain, by a BBRof a BIER domain, a BTL identifying a P2MP LSP within the BIER domain.The BTL identifying a P2MP LSP within the BIER domain may be obtained byreceiving the BTL identifying a P2MP LSP within the BIER domain,assigning the BTL identifying a P2MP LSP within the BIER domain, or thelike. At block 899, method 800 ends. It will be appreciated that variousother functions presented herein as being supported by EBBRs (e.g., aspresented in FIGS. 1-5) may be performed within the context of method800 of FIG. 8 or using one or more other methods which may be performedin conjunction with or independent of method 800 of FIG. 8.

It will be appreciated that, although embodiments for supportingMPLS-based multicast via a BIER domain are primarily presented hereinwithin the context of a specific type of multicast explicit replicationdomain (e.g., BIER), specific types of multicast protocols (e.g., MPLS)supporting specific types of multicast label switched paths (e.g., P2MPLSPs) based on specific types of multicast signaling protocols (e.g.,mLDP), various embodiments for supporting MPLS-based multicast via aBIER domain may be provided in conjunction with other types of multicastexplicit replication domains, other types of multicast protocols, othertypes of multicast label switched paths, other types of multicastsignaling protocols, or the like, as well as various combinationsthereof.

FIG. 9 depicts an example embodiment of a method for use by borderrouter of a multicast explicit replication domain for supportingassignment of a label to a multicast label switched path within themulticast explicit replication domain for uniquely identifying themulticast label switched path within the multicast explicit replicationdomain. It will be appreciated that, although primarily presented hereinas being performed serially, at least a portion of the functions ofmethod 900 may be performed contemporaneously or in a different orderthan as presented in FIG. 9. At block 901, method 900 begins. At block910, receive, by a border router of a multicast explicit replicationdomain from a multicast label switching domain, multicast signalinginformation associated with a multicast label switched path. At block920, send, by the border router toward a device configured to assign atree label identifying the multicast label switched path within themulticast explicit replication domain, the multicast signalinginformation associated with the multicast label switched path. At block999, method 900 ends. It will be appreciated that method 600 of FIG. 6may correspond to an embodiment of method 900 of FIG. 9 in which themulticast explicit replication domain is a BIER domain, the multicastlabel switching domain is an MPLS domain, the multicast signalinginformation is MPLS signaling information, the multicast label switchedpath is a P2MP LSP, and the tree label is a BDT for the P2MP LSP withinthe BIER domain.

FIG. 10 depicts an example embodiment of a method for use by anassigning node of a multicast explicit replication domain for supportingassignment of a label to a multicast label switched path within themulticast explicit replication domain for uniquely identifying themulticast label switched path within the multicast explicit replicationdomain. It will be appreciated that, although primarily presented hereinas being performed serially, at least a portion of the functions ofmethod 1000 may be performed contemporaneously or in a different orderthan as presented in FIG. 10. At block 1001, method 1000 begins. Atblock 1010, receive, by a device associated with a multicast explicitreplication domain, multicast signaling information associated with amulticast label switched path. At block 1020, assign, by the devicebased on the multicast signaling information associated with themulticast label switched path, a tree label identifying the multicastlabel switched path within the multicast explicit replication domain. Atblock 1099, method 1000 ends. It will be appreciated that method 700 ofFIG. 7 may correspond to an embodiment of method 1000 of FIG. 10 inwhich the multicast explicit replication domain is a BIER domain, themulticast signaling information is MPLS signaling information, themulticast label switched path is a P2MP LSP, and the tree label is a BDTfor the P2MP LSP within the BIER domain.

FIG. 11 depicts an example embodiment of a method for use by a borderrouter of a multicast explicit replication domain for supportingassignment of a label to a multicast label switched path within themulticast explicit replication domain for uniquely identifying themulticast label switched path within the multicast explicit replicationdomain. It will be appreciated that, although primarily presented hereinas being performed serially, at least a portion of the functions ofmethod 1100 may be performed contemporaneously or in a different orderthan as presented in FIG. 11. At block 1101, method 1100 begins. Atblock 1110, obtain, by a border router of a multicast explicitreplication domain, a tree label identifying a multicast label switchedpath within the multicast explicit replication domain. At block 1199,method 1100 ends. It will be appreciated that method 800 of FIG. 8 maycorrespond to an embodiment of method 1100 of FIG. 11 in which themulticast explicit replication domain is a BIER domain, the multicastlabel switched path is a P2MP LSP, and the tree label is a BDT for theP2MP LSP within the BIER domain.

Various embodiments for supporting MPLS-based multicast via a BIERdomain may provide various advantages or potential advantages. Variousembodiments for supporting MPLS-based multicast via a BIER domain may beconfigured to enable a network provider to deploy BIER in some segmentsof the network while retaining legacy multicast technology in othersegments of the network. Various embodiments for supporting MPLS-basedmulticast via a BIER domain may provide various other advantages orpotential advantages.

FIG. 12 depicts a high-level block diagram of a computer suitable foruse in performing various functions described herein.

The computer 1200 includes a processor 1202 (e.g., a central processingunit (CPU), a processor having a set of one or more processor cores, orthe like) and a memory 1204 (e.g., a random access memory (RAM), a readonly memory (ROM), or the like). The processor 1202 and the memory 1204are communicatively connected.

The computer 1200 also may include a cooperating element 1205. Thecooperating element 1205 may be a hardware device. The cooperatingelement 1205 may be a process that can be loaded into the memory 1204and executed by the processor 1202 to implement functions as discussedherein (in which case, for example, the cooperating element 1205(including associated data structures) can be stored on a non-transitorycomputer-readable storage medium, such as a storage device or otherstorage element (e.g., a magnetic drive, an optical drive, or thelike)).

The computer 1200 also may include one or more input/output devices1206. The input/output devices 1206 may include one or more of a userinput device (e.g., a keyboard, a keypad, a mouse, a microphone, acamera, or the like), a user output device (e.g., a display, a speaker,or the like), one or more network communication devices or elements(e.g., an input port, an output port, a receiver, a transmitter, atransceiver, or the like), one or more storage devices or elements(e.g., a tape drive, a floppy drive, a hard disk drive, a compact diskdrive, or the like), or the like, as well as various combinationsthereof.

It will be appreciated that computer 1200 of FIG. 12 may represent ageneral architecture and functionality suitable for implementingfunctional elements described herein, portions of functional elementsdescribed herein, or the like, as well as various combinations thereof.For example, computer 1200 may provide a general architecture andfunctionality that is suitable for implementing one or more of an MPLSrouter 114, a BIER router 115, MH 120, MS 130, BIER domain controller201, BIER domain controller 301, or the like, as well as variouscombinations thereof.

It will be appreciated that various functions presented herein may beimplemented in software (e.g., via implementation of software on one ormore processors, for executing on a general purpose computer (e.g., viaexecution by one or more processors) so as to provide a special purposecomputer, and the like) and/or may be implemented in hardware (e.g.,using a general purpose computer, one or more application specificintegrated circuits (ASIC), and/or any other hardware equivalents).

It will be appreciated that various functions presented herein may beimplemented within hardware, for example, as circuitry that cooperateswith the processor to perform various functions. Portions of thefunctions/elements described herein may be implemented as a computerprogram product wherein computer instructions, when processed by acomputer, adapt the operation of the computer such that the methodsand/or techniques described herein are invoked or otherwise provided.Instructions for invoking the various methods may be stored in fixed orremovable media (e.g., non-transitory computer-readable media),transmitted via a data stream in a broadcast or other signal bearingmedium, and/or stored within a memory within a computing deviceoperating according to the instructions.

It will be appreciated that the term “or” as used herein refers to anon-exclusive “or” unless otherwise indicated (e.g., use of “or else” or“or in the alternative”).

It will be appreciated that, although various embodiments whichincorporate the teachings presented herein have been shown and describedin detail herein, those skilled in the art can readily devise many othervaried embodiments that still incorporate these teachings.

What is claimed is:
 1. An apparatus, comprising: at least one processor;and at least one memory including a set of instructions; wherein the setof instructions is configured to, when executed by the at least oneprocessor, cause the apparatus to at least: receive, by a controllerassociated with a multicast explicit replication domain, multicastsignaling information associated with a multicast label switched path;and assign, by the controller based on the multicast signalinginformation associated with the multicast label switched path, a treelabel identifying the multicast label switched path within the multicastexplicit replication domain.
 2. The apparatus of claim 1, wherein themulticast signaling information is received from an ingress boundaryrouter of the multicast explicit replication domain.
 3. The apparatus ofclaim 1, wherein the multicast signaling information is received in asignaling packet of the multicast explicit replication domain.
 4. Theapparatus of claim 1, wherein the multicast signaling informationincludes a forwarding equivalence class and an action.
 5. The apparatusof claim 1, wherein the set of instructions is configured to, whenexecuted by the at least one processor, cause the apparatus to at least:send, from the device toward one or more border routers of the multicastexplicit replication domain interested in the multicast label switchedpath, the tree label identifying the multicast label switched pathwithin the multicast explicit replication domain.
 6. The apparatus ofclaim 5, wherein the one or more border routers of the multicastexplicit replication domain interested in the multicast label switchedpath include a border router of the multicast explicit replicationdomain from which the multicast signaling information is received and aborder router of multicast explicit replication domain at which packetsof the multicast label switched path enter the multicast explicitreplication domain.
 7. The apparatus of claim 1, wherein the set ofinstructions is configured to, when executed by the at least oneprocessor, cause the apparatus to at least: assign, by the controller, alabel identifying the multicast label switched path within a multicastdomain supported by the multicast explicit replication domain; and send,by the controller toward a root of the multicast label switched path viathe multicast domain, the label identifying the multicast label switchedpath within the multicast domain supported by the multicast explicitreplication domain.
 8. The apparatus of claim 1, wherein the multicastexplicit replication domain comprises a Bit Index Explicit Replication(BIER) domain and the tree label comprises a BIER tree label (BTL). 9.The apparatus of claim 1, wherein the multicast signaling informationcomprises Multiprotocol Label Switching (MPLS) signaling information andthe multicast label switched path comprises a point-to-multipoint (P2MP)label switched path (LSP).
 10. An apparatus, comprising: at least oneprocessor; and at least one memory including a set of instructions;wherein the set of instructions is configured to, when executed by theat least one processor, cause the apparatus to at least: receive, by aborder router of a multicast explicit replication domain from amulticast domain, a packet of a multicast label switched path, whereinthe packet includes a multicast label identifying the multicast labelswitched path within the multicast domain; perform, by the borderrouter, a modification of the packet to form a modified packet, whereinthe modification of the packet to form the modified packet includesremoving the multicast label identifying the multicast label switchedpath within the multicast domain and including a tree label identifyingthe multicast label switched path within the multicast explicitreplication domain; and send, by the border router toward the multicastexplicit replication domain, the modified packet.
 11. The apparatus ofclaim 10, wherein, to send the modified packet, the set of instructionsis configured to, when executed by the at least one processor, cause theapparatus to at least: encapsulate the modified packet within a headerof the multicast explicit replication domain to form a multicastexplicit replication domain packet; and send the multicast explicitreplication domain packet toward a router of the multicast explicitreplication domain.
 12. The apparatus of claim 11, wherein the headerincludes a bit string having a set of bit positions set in a mannerindicative of a set of egress nodes of the multicast explicitreplication domain to which the multicast explicit replication domainpacket is to be provided.
 13. The apparatus of claim 10, wherein the setof instructions is configured to, when executed by the at least oneprocessor, cause the apparatus to at least: receive, by the borderrouter of the multicast explicit replication domain, the tree labelidentifying the multicast label switched path within the multicastexplicit replication domain.
 14. The apparatus of claim 13, wherein thetree label identifying the multicast label switched path within themulticast explicit replication domain is received from a controller ofthe multicast explicit replication domain.
 15. The apparatus of claim10, wherein the set of instructions is configured to, when executed bythe at least one processor, cause the apparatus to at least: receive, bythe border router of the multicast explicit replication domain,multicast signaling information associated with a multicast labelswitched path; and assign, by the border router of the multicastexplicit replication domain based on the multicast signaling informationassociated with the multicast label switched path, the tree labelidentifying the multicast label switched path within the multicastexplicit replication domain.
 16. The apparatus of claim 10, wherein themulticast explicit replication domain comprises a Bit Index ExplicitReplication (BIER) domain and the tree label comprises a BIER tree label(BTL).
 17. The apparatus of claim 10, wherein the multicast domaincomprises a Multiprotocol Label Switching (MPLS) domain, wherein themulticast label comprises an MPLS label.
 18. An apparatus, comprising:at least one processor; and at least one memory including a set ofinstructions; wherein the set of instructions is configured to, whenexecuted by the at least one processor, cause the apparatus to at least:receive, by a border router of a multicast explicit replication domainassociated with a multicast domain, a multicast explicit replicationdomain packet including a packet of a multicast label switched path,wherein the packet of the multicast label switched path includes a treelabel identifying the multicast label switched path within the multicastexplicit replication domain; perform, by the border router, amodification of the packet of the multicast label switched path to forma modified packet, wherein the modification of the packet of themulticast label switched path includes removing the tree labelidentifying the multicast label switched path within the multicastexplicit replication domain and adding a multicast label identifying themulticast label switched path within the multicast domain; and send, bythe border router toward the multicast domain, the modified packet. 19.The apparatus of claim 18, wherein the multicast explicit replicationdomain packet encapsulates the packet of the multicast label switchedpath with a header that includes a bit string having a set of bitpositions set in a manner indicative of a set of egress nodes of themulticast explicit replication domain to which the multicast explicitreplication domain packet is to be provided.
 20. The apparatus of claim19, wherein the packet of the multicast label switched path is extractedfrom the multicast explicit replication domain packet based on adetermination that one of the bits in the bit string is set in a mannerindicative that the border router is one of the egress nodes ofmulticast explicit replication domain to which the multicast explicitreplication domain packet is to be provided.
 21. The apparatus of claim18, wherein the set of instructions is configured to, when executed bythe at least one processor, cause the apparatus to at least: receive, bythe border router of the multicast explicit replication domain, the treelabel identifying the multicast label switched path within the multicastexplicit replication domain.
 22. The apparatus of claim 21, wherein thetree label identifying the multicast label switched path within themulticast explicit replication domain is received from a controller ofthe multicast explicit replication domain.
 23. The apparatus of claim18, wherein the multicast explicit replication domain comprises a BitIndex Explicit Replication (BIER) domain and the tree label comprises aBIER tree label (BTL).
 24. The apparatus of claim 18, wherein themulticast domain comprises a Multiprotocol Label Switching (MPLS)domain, wherein the multicast label comprises an MPLS label.